1. Field of the Invention
The present invention relates to a microgyroscope with two resonant plates, and more particularly, to a microgyroscope in which the difference between the resonance frequencies of two resonant plates is greatly decreased.
2. Description of the Related Art
A resonant type gyroscope as disclosed in U.S. Pat. No. 5,892,153 includes two resonant plates having an independent resonance structure and a single spring serving both as a spring used in a driving mode and as a spring used in a sensing mode. In such conventional resonant type gyroscopes having two resonant plates, the thicknesses or weights of springs supporting the two resonant plates may differ due to, for example, a process error occurring during patterning for a vibratory structure, thereby causing the resonance frequencies of the two resonant plates to be different. Here, even the several Hz of difference between the resonance frequencies of the two resonant plates has a bad influence on the sensitivity of a gyroscope. To overcome this problem, a gyroscope with a single resonant plate has been proposed. However, in such a gyroscope, it is very difficult to separate an acceleration signal from a signal because the influence of acceleration cannot be removed from such a structure having a single resonant plate. To solve this problem, a torsion driving method and a two axial angular speed meter have been proposed. However, such method and meter creates interference between components in different directions (cross-axis sensitivity).
When a spring employing a bending mode is applied to a thick structure in order to detect the displacement in the direction perpendicular to a substrate, an error in the thickness of the spring causes a large variation in the spring constant. Thus, reproducibility of processes cannot be guaranteed. To solve this problem, a spring employing a torsion mode is used. However, since a torsion mode spring is short, thermal stress caused by transformation due to a change in temperature is concentrated on the spring, and thus the structure linked to the spring easily becomes unstable.
Meanwhile, the sensitivity of resonant type gyroscopes is best when a sensing frequency and a driving frequency are synchronized. For this reason, tuning is performed by adjusting a sensing frequency. However, in conventional resonant type gyroscopes including a gyroscope disclosed in U.S. Pat. No. 5,892,153 which embody a spring used in a driving mode and a spring used in a sensing mode in a single spring structure, an abnormal mode may take place due to, for example, large transformation of the spring. Due to such an abnormal mode, it is difficult to adjust the difference between a sensing frequency and a driving frequency to be 100 Hz or lower.
To solve the above problems, it is a first object of the present invention to provide a microgyroscope having resonant plates of which the difference between the resonance frequencies is greatly reduced.
It is a second object of the present invention to provide a microgyroscope with two resonant plates allowing an error in manufacturing to be reduced, thereby increasing reproducibility and yields.
It is a third object of the present invention to provide a microgyroscope with two resonant plates which can protect a mode coupling effect due to the interference between a driving mode and a sensing mode.
It is a fourth object of the present invention to provide a microgyroscope with two resonant plates which maintains high stability against thermal stress.
Accordingly, to achieve the above objects of the invention, in one embodiment, there is provided a microgyroscope with two resonant plates, which includes a substrate; first and second frames provided on the substrate to have a predetermined height, the first and second frames facing each other; a plurality of anchors supporting the first and second frames with respect to the substrate; first and second resonant plates provided between the first and second frames to be separated from each other by a predetermined distance; and a matching link unit connected to the first and second resonant plates so that it links the motion of one resonant plate to the motion of the other resonant plate such that the matching link unit is moved by the motion of one resonant plate in a first direction and then moves the other resonant plate in a second direction opposite to the first direction.
In this embodiment, the matching link unit comprises an actuating rod of which the center portion is fixed, a first connecting portion extended from one end of the actuating rod and connected to the first resonant plate, and a second connecting portion extended from the other end of the actuating rod and connected to the second resonant plate.
Each of the first and second frames comprises a sub frame extending toward the matching link unit, and the center portion of the actuating rod is supported by the sub frames.
The center portions of the first and second frames are connected to the anchors through sensing beams. The sensing beams are formed at the center portions of the first and second frames, respectively, and connected to the anchors provided by the center portions of the first and second frames, respectively.
Each of the sensing beams in the first and second frames includes a buffer portion for alleviating stress. The buffer portion of the sensing beam is a loop type having a through portion at the center thereof.
The first and second resonant plates are connected to the first and second frames, respectively, by driving beams for a driving mode. Each of the driving beams has a portion extending in a direction in which a corresponding first or second resonant plate resonates and extending in a direction perpendicular to the resonance direction.
In another embodiment, there is provided a microgyroscope with two resonant plates, which includes substrate; first and second frames provided on the substrate to have a predetermined height, the first and second frames facing each other; a plurality of anchors supporting the center portions of the first and second frames, respectively, with respect to the substrate; sensing beams provided between the anchors and the first and second frames; first and second resonant plates provided between the first and second frames to be separated from each other by a predetermined distance; driving beams for connecting the first and second frames to the first and second resonant plates, respectively; and a matching link unit connected to the first and second resonant plates so that it can make the motion of one resonant plate bound to the motion of the other resonant plate such that the matching link unit is moved by the motion of one resonant plate in a first direction and then moves the other resonant plate in a second direction opposite to the first direction.
In this embodiment, the matching link unit includes an actuating rod of which the center portion is fixed, a first connecting portion extended from one end of the actuating rod and connected to the first resonant plate, and a second connecting portion extended from the other end of the actuating rod and connected to the second resonant plate. Each of the first and second frames includes a sub frame extending toward the matching link unit, and the center portion of the actuating rod is supported by the sub frames.
The sensing beams are formed at the center portions of the first and second frames, respectively, and connected to the anchors provided by the center portions of the first and second frames, respectively.
Each of the sensing beams in the first and second frames comprises a buffer portion for alleviating stress. The buffer portion of the sensing beam is a loop type having a through portion at the center thereof.
Each of the driving beams has a portion extending in a direction in which a corresponding first or second resonant plate resonates and extending in a direction perpendicular to the resonance direction.